(i)[5]
Show that the angle $BAC$ is $\cos^{-1}\left(\frac{1}{3}\right)$.
(ii)[3]
Use the result in part (i) to determine the exact area of triangle $ABC$.
Mathematics 9709 · AS & A Level · Trigonometry
Trigonometry — practice question
The position vectors of points $A$, $B$ and $C$ with respect to an origin $O$ are $\overrightarrow{OA} = \begin{pmatrix} 2 \\ 1 \\ 3 \end{pmatrix}$, $\overrightarrow{OB} = \begin{pmatrix} 6 \\ -1 \\ 7 \end{pmatrix}$ and $\overrightarrow{OC} = \begin{pmatrix} 2 \\ 4 \\ 7 \end{pmatrix}$.
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